Apply FlateDecode filter to streams

VAR.PdfTools.Workbench/FrmPdfInfo.cs

@@ -72,7 +72,7 @@ namespace VAR.PdfTools.Workbench
             {
                 string.Format("Number of Objects: {0}", nObjects),
                 string.Format("Number of Streams: {0}", nStreams),
-                string.Format("Stream Filters: {0}", string.Join(", ", streamFilters.Distinct().ToArray())),
+                string.Format("Unsuported Stream Filters: {0}", string.Join(", ", streamFilters.Distinct().ToArray())),
             };
 
         }

VAR.PdfTools/PdfDocument.cs

@@ -1,5 +1,6 @@
 using System.Collections.Generic;
 using System.IO;
+using System.IO.Compression;
 
 namespace VAR.PdfTools
 {
@@ -23,6 +24,41 @@ namespace VAR.PdfTools
 
         #endregion
 
+        #region Private methods
+
+        private static byte[] DecodeFlateStreamData(byte[] streamData)
+        {
+            MemoryStream msInput = new MemoryStream(streamData);
+            MemoryStream msOutput = new MemoryStream();
+
+            // It seems to work when skipping the first two bytes.
+            byte header;   // 0x30 0x59
+            header = (byte)msInput.ReadByte();
+            //Debug.Assert(header == 48);
+            header = (byte)msInput.ReadByte();
+            //Debug.Assert(header == 89);
+            DeflateStream zip = new DeflateStream(msInput, CompressionMode.Decompress, true);
+            int cbRead;
+            byte[] abResult = new byte[1024];
+            do
+            {
+                cbRead = zip.Read(abResult, 0, abResult.Length);
+                if (cbRead > 0)
+                    msOutput.Write(abResult, 0, cbRead);
+            }
+            while (cbRead > 0);
+            zip.Close();
+            msOutput.Flush();
+            if (msOutput.Length >= 0)
+            {
+                msOutput.Capacity = (int)msOutput.Length;
+                return msOutput.GetBuffer();
+            }
+            return null;
+        }
+
+        #endregion
+
         #region Public methods
 
         public static PdfDocument Load(string filename)
@@ -43,6 +79,25 @@ namespace VAR.PdfTools
                     doc.Objects.Add(obj);
                 }
             } while (parser.IsEndOfStream() == false);
+
+            // Apply filters to streams
+            foreach(PdfObject obj in doc.Objects)
+            {
+                if(obj.Data.Type != PdfElementTypes.Stream) { continue; }
+                PdfStream stream = obj.Data as PdfStream;
+
+                string filter = stream.GetParamAsString("Filter");
+                if (filter == "FlateDecode")
+                {
+                    stream.OriginalData = stream.Data;
+                    stream.OriginalFilter = stream.Dictionary.Values["Filter"];
+                    byte[] decodedStreamData = DecodeFlateStreamData(stream.Data);
+                    stream.Data = decodedStreamData;
+                    stream.Dictionary.Values["Length"] = new PdfInteger { Value = decodedStreamData.Length };
+                    stream.Dictionary.Values.Remove("Filter");
+                }
+            }
+
             return doc;
         }
 

VAR.PdfTools/PdfElements.cs

@@ -84,6 +84,29 @@ namespace VAR.PdfTools
         public PdfElementTypes Type { get; private set; } = PdfElementTypes.Stream;
         public PdfDictionary Dictionary { get; set; }
         public byte[] Data { get; set; }
+
+        public byte[] OriginalData { get; set; }
+        public IPdfElement OriginalFilter { get; set; }
+
+        public string GetParamAsString(string name)
+        {
+            if(Dictionary.Values.ContainsKey(name) == false) { return null; }
+
+            IPdfElement value = Dictionary.Values[name];
+            if (value is PdfArray)
+            {
+                value = ((PdfArray)value).Values[0];
+            }
+            if (value is PdfName)
+            {
+                return ((PdfName)value).Value;
+            }
+            if (value is PdfString)
+            {
+                return ((PdfString)value).Value;
+            }
+            return null;
+        }
     }
 
     public class PdfObject : IPdfElement